Variable displacement vane pump with variable target regulator

ABSTRACT

A variable displacement vane-type fluid pump is provided which permits improved regulation of the pump discharge such that the pump can meet the various requirements of lubrication for internal combustion engines at all speeds with minimized use of power. Of course, the vane pump may also be utilized in a wide range of power transmission and other fluid distribution applications. The variable displacement vane pump of the invention may utilize both hydrostatic and mechanical assistance in radially positioning its vanes to ensure efficient and quiet operation of the pump and to facilitate priming of the pump. The vane pump of the invention may also use both hydrostatic and mechanical actuators to control the position of its containment ring or eccentric ring and hence, regulate the output of the pump. According to yet another aspect of the present invention, to prevent inlet flow restriction or cavitation, a valve may be provided to permit some of the pump outlet or discharge flow to bleed into the pump inlet to provide needed velocity and energy to the fluid flow into the pump inlet.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/255,629, titled “Variable Displacement Pump and Method,” filedDec. 12, 2000.

FIELD OF THE INVENTION

This invention relates generally to fluid pumps and more particularly toa variable displacement vane pump.

BACKGROUND OF THE INVENTION

Hydraulic power transmission assemblies and fluid distribution systemsmay utilize a vane-type pump. Such pumps typically have a rotor with aplurality of circumferentially spaced vanes rotatably carried by therotor and slidable relative thereto in slots provided in the rotor. Therotor and vanes cooperate with the internal contour of a containmentring or eccentric ring eccentrically mounted relative to an axis of therotor and vanes to create fluid chambers between the containment ring oreccentric ring, rotor and vanes. Due to the eccentricity between thecontainment ring or eccentric ring and the rotor and vanes, the fluidchambers change in volume as they are moved with the rotating rotor andbecome larger in volume as they are moved across an inlet port andsmaller in volume across an outlet port. To vary the eccentricitybetween the containment ring or eccentric ring and the rotor, thecontainment ring or eccentric ring may be pivoted upon a fixed axis in apump housing. Pivoting the containment ring or eccentric ring varies thechange in volume of the fluid chambers in use of the pump and hence,varies the displacement characteristic of the pump.

Side plates carried by the pump housing enclose the containment ring oreccentric ring, the rotor and the vanes, and provide passages throughwhich fluid flows to and from the rotor and vanes. These passages, alongwith timing grooves and the containment ring or eccentric ring contourdefine pump cycles or zones, namely a fill or inlet zone, aprecompression zone from the inlet to the outlet, a displacement ordischarge zone, and a decompression zone from the outlet to the inlet.

In current vane-type pumps, the containment ring or eccentric ring ispivoted and oriented by a fluid pressure signal applied to a piston ordirectly to the containment ring which pivots the containment ring oreccentric ring against the bias of a fixed spring. In other words, asingle fluid pressure signal is used to pivot the containment ring oreccentric ring. Accordingly, the control of the containment ring oreccentric ring is essentially limited to a pressure relief type controlwherein the containment ring or eccentric ring is pivoted against thebias of the spring only when a sufficient pressure is applied to thepiston or containment ring or eccentric ring. When the fluid pressureapplied to the piston is not sufficient to move the containment ring oreccentric ring against the bias of a fixed spring, the position of thecontainment ring or eccentric ring is determined by the spring whichlimits to one regulation profile characteristic.

Additionally, it has been recognized that for efficient and quietoperation of a vane-type pump it is desirable to maintain the vanes incontinuous contact with the containment ring or eccentric ring. Somevane-type pumps depend upon centrifugal force to maintain the contactbetween the vanes and the containment ring or eccentric ring. Thesepumps may lack positive and continuous contact between the vane andcontainment ring or eccentric ring resulting in adverse wear anddecreased pump performance. One method to improve the contact betweenthe vanes and the containment ring or eccentric ring involves applying adischarge fluid pressure to chambers or slots in the rotor in which thevanes are received. The fluid pressure drives the vanes radiallyoutwardly and into contact with the containment ring or eccentric ring.However, in at least some conditions, the vanes have a tendency toremain in the rotor slots and the centrifugal force of the spinningrotor is not sufficient to overcome the viscous drag force on the vanes.Without the vanes extending radially outwardly from the rotor, therotating rotor displaces little if any fluid such that there is littleor no discharge pressure. Accordingly, there is little or no dischargepressure communicated to the vane slots and tending to force the vanesradially outwardly from the rotor. Hence, the pump will not prime.

SUMMARY OF THE INVENTION

A variable displacement vane-type fluid pump is provided which has aregulated discharge controlled at least in part by a pair of pilotpressure signals. Desirably, the vane pump of the invention permitsimproved regulation of the pump discharge such that the pump can meetthe various requirements of lubrication for internal combustion enginesat all speeds. Of course, the vane pump may also be utilized in powertransmission and other fluid distribution applications. The variabledisplacement vane pump of the invention may utilize both hydrostatic andmechanical assistance in radially positioning its vanes to ensureefficient and quiet operation of the pump and to facilitate priming ofthe pump. The vane pump of the invention may also use both hydrostaticand mechanical actuators to control the position of its containment ringor eccentric ring and hence, regulate the output of the pump. Accordingto yet another aspect of the present invention, to prevent inlet flowrestriction or cavitation, a valve may be provided to permit some of thepump outlet or discharge flow to exhaust into the pump inlet to provideneeded velocity energy to the fluid flow in the pump inlet.

To achieve the dual pilot pressure regulation of the pump output thevane pump has a pair of actuators each operable to position thecontainment ring or eccentric ring as desired. In one embodiment of theinvention, the actuators are opposed pistons that are each actuated by aseparate pilot pressure signal to pivot the cam as a function of thepressure signals. In another embodiment, a seal may be provided betweenthe containment ring or eccentric ring and the pump housing definingseparate chambers, the chambers receive pressurized fluid bearingdirectly on the containment ring or eccentric ring to position it andfunction as the actuators without any pistons between the fluid signaland the containment ring or eccentric ring. In any of the embodiments,the cam may be biased in one or both directions of its pivotal movement,such as by one or more springs.

To ensure priming of the pump and development of discharge pressure, oneor more rings lie adjacent to the rotor radially inwardly of the vanesto ensure that at least some of the vanes extend radially outwardlybeyond the rotor and in contact with the contoured ring at all times.Preferably, hydrostatic pressure is employed in chambers behind thevanes to provide full extension of the vanes and maintain them incontinuous contact with the containment ring or eccentric ring.

Accordingly, some of the objects, features and advantages of thisinvention include providing an eccentric vane pump which enablesimproved control of the pump discharge, ensures priming of the pump,reduces inlet flow restriction and cavitation, enables pressure signalsfrom two or more points in the hydraulic circuit to be used to regulatepump discharge, strategically positions the cam and its pivot tominimize movement in the direction perpendicular to the desireddirection of movement of the eccentric ring as it pivots, is ofrelatively simple design and economical manufacture and assembly, isdurable, reliable and has a long and useful life in service.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of this invention willbe apparent from the following detailed description of the preferredembodiments, appending claims and accompanying drawings in which:

FIG. 1 is a perspective view of a variable displacement eccentric vanepump according to the present invention;

FIG. 2 is a perspective view of the vane pump of FIG. 1 with a sideplate removed to show the internal components of the pump;

FIG. 3 is a plan view of the pump as in FIG. 2 illustrating thecontainment ring or eccentric ring in its zero-displacement position;

FIG. 4 is a plan view of the pump as in FIG. 2 illustrating thecontainment ring or eccentric ring in its maximum-displacement position;

FIG. 5 is a diagrammatic sectional view of a variable target dual pilotregulation valve which pivots the containment ring or eccentric ring ofthe pump according to one aspect of the present invention;

FIG. 6 is an enlarged, fragmentary sectional view illustrating a portionof the rotor and a vane according to the present invention;

FIG. 7 is an enlarged, fragmentary sectional view of the rotor and vaneillustrating a seal between the vane and rotor when the vane is tiltedwithin its slot in the rotor;

FIG. 8 is a schematic representation of the hydraulic circuit of thevane pump of an embodiment of this invention including completing a3-way variable target dual pilot regulation valve;

FIG. 9 is a schematic representation of the hydraulic circuit of a vanepump according to the present invention including a 3-way regulationvalve and an anti-cavitation valve; and

FIG. 10 is a diagrammatic view of the containment ring or eccentric ringof the vane pump in its zero-displacement and maximum-displacementpositions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring in more detail to the drawings, FIGS. 1-3 illustrate avariable displacement vane pump 10 having a rotor 12 and associatedvanes 14 driven for rotation to draw fluid through a pump inlet 16,increase the pressure of the fluid, and discharge the fluid underpressure from an outlet 18 of the pump 10. A containment ring oreccentric ring 20 is carried by a housing 22 of the pump 10 and ispivoted relative to the rotor 12 to vary the displacement of the pump.Such a pump 10 is widely used in a plurality of fluid applicationsincluding engine lubrication and power transmission applications.

The housing 22 preferably comprises a central body 24 defining aninternal chamber 26 in which the containment ring or eccentric ring 20and rotor 12 are received. The housing 22 further includes a pair of endplates 28,30 on opposed, flat sides of the central body 24 to enclosethe chamber 26. A groove 32 formed in an internal surface 34 of thecentral body 24 is constructed to receive a pivot pin 36 between thecontainment ring or eccentric ring 20 and housing 22 to permit andcontrol pivotal movement of the containment ring or eccentric ring 20relative to the housing 22. Spaced from the groove 32 and preferably ata generally diametrically opposed location, a seat surface 38 isprovided in the central body 24. The seat surface 38 is engageable withthe containment ring or eccentric ring 20 in at least certain positionsof the containment ring or eccentric ring to provide a fluid tight sealbetween them. One or both of the containment ring or eccentric ring 20and central body 24 may carry an elastomeric or other type seal 40 thatdefines at least in part the seat surface.

The containment ring or eccentric ring 20 is annular having an opening41 and is received within the chamber 26 of the housing 22. Thecontainment ring or eccentric ring 20 has a groove 42 in its exteriorsurface which receives in part the pivot pin 36 to permit pivotalmovement between the containment ring or eccentric ring 20 and centralbody 24. Such pivotal movement of the containment ring or eccentric ring20 is limited by engagement of the exterior surface of the containmentring or eccentric ring 20 with the interior surface 34 of the centralbody 24. As viewed in FIGS. 4 and 10, the containment ring or eccentricring 20 is pivoted counterclockwise into engagement with the housing 22in its first position wherein the pump 10 has its maximum displacement.As best shown in FIGS. 3 and 10, the containment ring or eccentric ring20 may be pivoted clockwise from its first position to a second positionin which the pump 10 has its minimum displacement. Of course, thecontainment ring or eccentric ring 20 may be operated in any orientationbetween and including its first and second positions to vary thedisplacement of the pump, as desired. The containment ring or eccentricring 20 has an internal surface which is generally circular, but may becontoured or off-centered to improve or alter the pump 10 performance.The containment ring or eccentric ring 20 may also have a second groove44 in its exterior surface adapted to carry the seal 40 engageable withthe internal surface 34 of the central body 24 to provide a fluid tightseal between the containment ring or eccentric ring 20 and central body24. The fluid tight seal essentially separates the chamber 26 into twoportions 26 a, 26 b on either side of the seal to enable a pressuredifferential to be generated between the separated chamber portions 26a, 26 b. The pressure differential may be used to pivot the containmentring or eccentric ring 20 between or to its first and second positionsto control the pump displacement.

To move fluid through the pump 10, a rotating displacement group 50 isprovided in the housing 22. The rotating displacement group 50 comprisesa central drive shaft 52, the rotor 12 which is carried and driven forrotation by the drive shaft 52, and a plurality of vanes 14 slidablycarried by the rotor 12 for co-rotation with the rotor 12. The driveshaft 52 is fixed in position for rotation about its own axis 53. Therotor 12 is fixed to the drive shaft 52 for co-rotation therewith aboutthe axis of the shaft 52.

As shown, the rotor 12 is a generally cylindrical member having aplurality of circumferentially spaced apart and axially and radiallyextending slots 54 that are open to an exterior surface 56 of the rotor12 and which terminate inwardly of the exterior surface 56. Each slot 54is constructed to slidably receive a separate vane 14 so that the vanesare movable relative to the rotor 12 between retracted and extendedpositions. Each slot 54 in the rotor 12 preferably terminates at a smallchamber 58 constructed to receive pressurized fluid. The pressurizedfluid in a chamber 58 acts on the vane 14 in the associated slot 54 tocause the vane 14 to slide radially outwardly until it engages theinternal surface 34 of the containment ring or eccentric ring 20.Preferably, during operation of the pump 10, the fluid pressure withinthe chamber 58 and slot 54 is sufficient to maintain substantiallycontinuous contact between the vanes 14 and the internal surface of thecontainment ring or eccentric ring 20.

In accordance with one aspect of the present invention, a vane extensionmember 60 is movably positioned on the rotor 12 to engage one or more ofthe vanes 14 and cause such vanes 14 to extend radially outwardly beyondthe periphery of the rotor 12. This facilitates priming the pump 10 byensuring that at least two of the vanes 14 extend beyond the peripheryof the rotor 12 at all times. Without the extension member 60 the vanes14 may tend to remain in their retracted position, not extending beyondthe exterior 56 of the rotor 12, such that subsequent turning of therotor 12 without any vanes 14 extending outwardly therefrom, does notdisplace sufficient fluid to prime the pump 10 and increase the pumpoutput pressure. Accordingly, no fluid pressure is generated in thechambers 58 or slots 54 of the rotor 12 and therefore no pressure actson the vanes 14 causing them to extend outwardly and the pump 10 willnot prime. Such a condition may be encountered, for example, in mobileand automotive applications when starting a cold vehicle in cold weathersuch as during a cold start of an automobile.

In the embodiment shown in FIG. 2, the vane extension member 60 is aring slidably received in an annular recess 62 formed in an end face ofthe rotor 12 and having a diameter sufficient to ensure that at leasttwo of the vanes 14 extends beyond the periphery of the rotor 12 at alltimes. The recess 62 provides an outer shoulder 64 and an inner shoulder66 between which the ring 60 may slide. The ring 60 slides in the recess62 when acted on by vanes 14 which are radially inwardly displaced viaengagement with the containment ring or eccentric ring 20 therebypushing the ring 60 towards the diametrically opposed vanes 14 causingthem to extend beyond the periphery of the rotor 12. The ring 60 isretained between the rotor 12 and the adjacent side plate of the housing22 in assembly of the pump 10. A second ring may be provided on theopposite face of the rotor, if desired.

Desirably, as shown in FIGS. 6 and 7, the slots 54 in the rotor 12 aresized to permit a fluid film to form on the leading and trailing faces68, 69 of each vane 14. The fluid film supports the vanes 14 as therotor 12 rotates. The fluid film prevents a wear of the fluid sloteffectively seating a bearing surface. Additionally, the size of theslots 54 is desired to prevent vane tilt while still slowing fluid toenter a contact seal between the rotor 12 and vanes 14 in the areas oftheir contact should vane tilting occur, to the extent that any vanetilting is present. The contact seals maintain the pressurized fluidacting on the vanes 14 and prevents it from leaking or flowing out ofthe slots 54. Such leakage is otherwise likely to occur due to thepressure differential between the fluid in the chambers 58 and slots 54which is at pump outlet pressure and lower pressure portions of the pumpcycle (nearly all but at the outlet of the pump). By preventing thisleakage, it is ensured that a sufficient hydrostatic force biases thevanes 14 radially outwardly toward the containment ring or eccentricring 20 to improve the continuity of the contact between the vanes 14and the containment ring or eccentric ring 20.

To displace fluid, the containment ring or eccentric ring 20 is mountedeccentrically relative to the drive shaft 52 and rotor 12. Thiseccentricity creates a varying clearance or gap between the containmentring or eccentric ring 20 and the rotor 12. The varying clearing createsfluid pumping chambers 70, between adjacent vanes 14, the rotor 12 andthe internal surface of the containment ring or eccentric ring 20, whichhave a variable volume as they are rotated in use. Specifically, eachpumping chamber 70 increases in volume during a portion of itsrotational movement, thereby creating a drop in pressure in that pumpingchamber 70 tending to draw fluid therein. After reaching a maximumvolume, each pumping chamber 70 then begins to decrease in volumeincreasing the pressure therein until the pumping chamber is registeredwith an outlet and fluid is forced through said outlet at the dischargepressure of the pump 10. Thus, the eccentricity provides enlarging anddecreasing pumping chambers 70 which provide both a decreased pressureto draw fluid in through the inlet of the pump 10 and thereafterincrease the pressure of the fluid and discharge it from the outlet ofthe pump 10 under pressure.

The degree of the eccentricity determines the operationalcharacteristics of the pump 10, with more eccentricity providing higherflow rate of the fluid through the pump 10 and less eccentricityproviding a lower flow rate in pressure of the fluid. In a so-called“zero displacement position” or the second position of the containmentring or eccentric ring 20 shown in FIG. 3, the opening 41 is essentiallycoaxially aligned with the rotor 12 so that the fluid pumping chambers70 have an essentially constant volume throughout their rotation. Inthis orientation, the pumping chambers 70 do not enlarge to draw flowtherein nor do they become smaller in volume to increase the pressure offluid therein creating a minimum performance condition or a zerodisplacement condition of the pump 10. When the containment ring oreccentric ring 20 is in its first or maximum displacement position thepumping chambers 70 vary in size between their maximum volume andminimum volume as the rotor 12 rotates providing increased pumpdisplacement.

As shown in FIGS. 3 and 4, to control the pivoting and location of thecontainment ring or eccentric ring 20 a pair of pistons 72, 74 may beutilized with the pistons 72, 74 operable in opposed directions to pivotthe containment ring or eccentric ring 20 between its first and secondpositions. Desirably, each piston 72, 74 may be responsive to differentfluid pressure signals that may be taken from two different points inthe fluid circuit, one of which must come from the regulating valve.Accordingly, two different portions of the fluid circuit may be used tocontrol the displacement of the containment ring or eccentric ring 20,and hence the operation and displacement of the pump 10. The pistons 72,74 may be of different sizes as desired to vary the force on the pistonsfrom the pressurized fluid signals. Further, one or both of the pistons72, 74 may be a spool type valve biased by a spring, or other mechanismto aid in controlling the movement of the containment ring or eccentricring 20 and operation of the pump. As an alternative, if a seal 40 isprovided between the containment ring or eccentric ring 20 and housing22, a controlled volume of fluid under pressure may be disposed directlyin the chamber portions 26 a, 26 b defined on opposite sides of the seal40. Fluid at different volumes and pressures may be provided on eitherside of the seal 40 to control the movement of the containment ring oreccentric ring 20. Of course, any combination of these actuators may beused to control the movement and position of the containment ring oreccentric ring 20 in use of the pump 10.

Desirably, as best shown in FIG. 10, in accordance with a further aspectof the present invention, the axis 76 about which the containment ringor eccentric ring 20 is pivoted is located to provide an essentiallylinear movement of the containment ring or eccentric ring 20 between itsfirst and second positions. To do so, the containment ring or eccentricring 20 is pivoted about an axis 76 which is offset from the drive shaftaxis 53 by one-half of the distance of travel in the direction ofeccentricity of the containment ring or eccentric ring 20 between itsfirst and second positions. In other words, the pivot axis 76 of thecontainment ring or eccentric ring 20 is offset from the drive shaftaxis 53 by one-half of the maximum eccentricity of the containment ringor eccentric ring 20 relative to the drive shaft axis 53, and hence,relative to the rotor 12. The pivoting movement of the containment ringor eccentric ring 20 occurs along an at least somewhat arcuate path. Bypositioning the pivot axis 76 of the containment ring or eccentric ring20 as described, the path of movement of the containment ring oreccentric ring 20 becomes essentially linear between its first andsecond positions. Non-linear or compound movement of the containmentring or eccentric ring 20 affects the gap or clearance between the rotor12 and the containment ring or eccentric ring 20. The performance andoperating characteristics of the pump 10 are influenced by this gap orclearance. Accordingly, the non-linear movement of the containment ringor eccentric ring 20 when it is pivoted can vary the size of the fluidchambers throughout the pump 10, and importantly, in the area of theinlet 16 and outlet 18 of the pump. For example, the pumping chambers 70may become slightly larger in volume as they approach the outlet 18reducing the pressure of fluid therein and causing inefficientpressurization of the fluid at the discharge port. Desirably, offsettingthe pivot axis 76 of the containment ring or eccentric ring 20 inaccordance with this invention provides a movement of the containmentring or eccentric ring 20 which reduces such centrality errors andfacilitates control of the pump operating characteristics to improvepump performance and efficiency. The arrangement of the invention alsopermits a more simple pump design with a center point of the containmentring or eccentric ring opening 41 moving along an essentially linearpath. Further, the pump 10 should operate with less airborne or fluidborne noise.

Preferably, to control the application of fluid pressure signals to theactuators that in turn control the movement of the containment ring oreccentric ring 20, a single control valve 80 reacts to two pilotpressure signals and their application to the actuators. As shown inFIG. 5, the control valve 80 has a spool portion 82 with a plurality ofannular grooves and lands between adjacent grooves providing sealingengagement with a bore 84 in which the spool portion 82 is received. Thevalve 80 also has a piston portion 86 comprising an outer sleeve 88 andan inner piston 90 slidably carried by the sleeve 88. A first spring 92is disposed between the plunger 90 and the spool portion 82 to yieldablybias the position of the spool portion 82 and a second spring 94 isdisposed between the sleeve 88 and the plunger 90 to yieldably bias theplunger 90 away from the sleeve 88.

As shown in FIGS. 5 and 8, the valve 80 has a first inlet 96 throughwhich fluid discharged from the pump 10 is communicated with a chamber98 in which the plunger 90 is received to provide a force acting on theplunger 90 in a direction opposing the biasing force of the secondspring 94. A second inlet 100 communicates fluid discharged from thepump 10 with the spool portion 82. A third inlet 102 communicates fluidpressure from a downstream fluid circuit source from a second portion ofthe fluid circuit with a chamber 104 defined between the plunger 90 andouter sleeve 88. A fourth inlet 106 communicates the second portion ofthe fluid circuit with an end 108 of the spool portion 82 locatedopposite the plunger 90. In addition to the inlets, the valve 80 has afirst outlet 110 communicating with a sump or reservoir 112, a secondoutlet 114 communicating with the first actuator 74, and a third outlet116 communicating with the second actuator 72. As discussed above, thefirst and second actuators 72, 74 control movement of the containmentring or eccentric ring 20 to vary the displacement of the pump 10.

In more detail, the plunger 90 has a cylindrical body 120 with a blindbore 122 therein to receive and retain one end of the first spring 92.An enlarged head 124 at one end of the plunger 90 is closely slidablyreceived in the chamber 98, which may be formed in, for example, thepump housing 22, and is constructed to engage the outer sleeve 88 tolimit movement of the plunger 90 in that direction. The outer sleeve 88is preferably press-fit or otherwise fixed against movement in thechamber 98. The outer sleeve 88 has a bore 126 which slidably receivesthe body 120 of the plunger 90, a radially inwardly extending rim 128 atone end to limit movement of the spool portion 82 toward the plunger 90,and a reduced diameter opposite end 130 defining the annular chamber 104in which the second spring 94 is received. The annular chamber 104 mayalso receive fluid under pressure which acts on the plunger 90.

The spool portion 82 is generally cylindrical and is received in thebore 84 of a body, such as the pump housing 22. The spool portion 82 hasa blind bore 132, is open at one end 134 and is closed at its other end108. A first recess 136 in the exterior of the spool portion 82 leads toone or more passages 139 which open into the blind bore 132. The firstrecess 136 is selectively aligned with the third outlet 116 to permitthe controlled volume of pressurized fluid, keeping the displacementhigh at the second actuator 72 (chamber 26 a) to vent back through thespool portion 82 via the first recess 136, corresponding passages 139blind bore 132 and the first outlet 110 leading to the sump or reservoir112. This reduces the volume and pressure of fluid at the secondactuator 72 (chamber 26 a). Likewise, the spool portion 82 has a secondrecess 140 which leads to corresponding passages 142 opening into theblind bore 132 and which is selectively alignable with the second outlet114 to permit fluid controlled volume of pressurized fluid, keeping thedisplacement low at the first actuator 74 (chamber 26 b) to vent backthrough the valve 80 via the second recess 140, corresponding passages142, blind bore 132 and first outlet 110 to the sump or reservoir 112.

The spool portion 82 also has a third recess 144 disposed between thefirst and second recesses 136, 140 and generally aligned with the secondinlet 100. The third recess 144 has an axial length greater than thedistance between the second inlet 100 and the second outlet 114 andgreater than the distance between the second inlet 100 and the thirdoutlet 116. Accordingly, when the spool portion 82 is sufficientlydisplaced toward the plunger portion 86, the third recess 144communicates the second outlet 114 with the second inlet 100 to enablefluid at discharge pressure to flow through the second outlet 114 fromthe second inlet 100. This increases the volume and pressure of fluidacting on the first actuator 74. Likewise, when the spool portion 82 isdisplaced sufficiently away from the plunger portion 86, the thirdrecess 144 communicates the second inlet 100 with the third outlet 116to permit fluid at pump discharge pressure to flow through the thirdoutlet 116 from the second inlet 100. This increases volume and pressureof fluid acting on the second actuator 72. From the above it can be seenthat displacement of the spool portion 82 controls venting of thedisplacement control chamber through the first and second recesses 136,140, respectively, when they are aligned with the second and thirdoutlets 114, 116, respectively. Displacement of the spool portion 82also permits charging or increasing of the pilot pressure signalsthrough the third recess 144 when it is aligned with the second andthird outlets 114, 116, respectively.

Desirably, the displacement of the spool portion 82 may be controlled atleast in part by two separate fluid signals from two separate portionsof the fluid circuit. As shown, fluid at pump discharge pressure isprovided to chamber 98 so that it is applied to the head 124 of theplunger 90 and tends to displace the plunger 90 toward the spool portion82. This provides a force (transmitted through the first spring 92)tending to displace the spool portion 82. This force is countered, atleast in part, by the second spring 94 and the fluid pressure signalfrom a second point in the fluid circuit which is applied to the distalend 108 of the spool portion 82 and to the chamber 104 between the outersleeve 88 and plunger 90 which acts on the head 124 of the plunger 90 ina direction tending to separate the plunger from the outer sleeve. Themovement of the spool portion 82 can be controlled as desired bychoosing appropriate springs 92, 94, fluid pressure signals and/orrelative surface areas of the plunger head 124 and spool portion end 108upon which the pressure signals act. Desirably, to facilitatecalibration of the valve 80, the second spring 94 may be selected tocontrol the initial or at rest compression of the first spring 92 tocontrol the force it applies to the spool portion 82 and plunger 90.

In response to these various forces provided by the springs 92, 94 andthe fluid pressure signals acting on the plunger 90 and the spoolportion 82, the spool portion 82 is moved to register desired recesseswith desired inlet or outlet ports to control the flow of fluid to andfrom the first and second actuators 72, 74 (or chamber 26 a/26 b). Morespecifically, as viewed in FIG. 5, when the spool portion 82 is drivendownwardly, the third recess 144 bridges the gap between the secondinlet 100 and the third outlet 116 so that pressurized fluid dischargedfrom the pump 10 is provided to the second actuator 72. This movement ofthe spool portion 82 preferably also aligns the second recess 140 withthe second outlet 114 to vent the volume and pressure of fluid at thefirst actuator 74 to the sump or reservoir 112. Accordingly, thecontainment ring or eccentric ring 20 will be displaced by the secondactuator 72 toward its first position increasing the displacement of thepump 10. The spool 82 operates with the bore 84 and outlets to behave aswhat is commonly known as a “4-way directional valve.” As the spoolportion 82 is driven upwardly, as viewed in FIG. 5, the third recess 144will bridge the gap between the second inlet 100 and the second outlet114 providing fluid at pump discharge pressure to the first actuator 74.This movement of the spool portion 82 preferably also aligns the firstrecess 136 with the third outlet 116 to vent the volume of and pressureof fluid at the second actuator 72 to the sump or reservoir 112.Accordingly, the containment ring or eccentric ring 20 will be movedtoward its second position decreasing the displacement of the pump 10.In this manner, the relative controlled volume and pressures arecontrolled by two separate pressure signals which may be taken from twodifferent portions of the fluid circuit. In the embodiment shown, afirst pressure signal is the fluid discharged from the pump 10 and asecond pressure signal is from a downstream fluid circuit source. Inthis manner, the efficiency and performance of the pump can be improvedthrough more capable control.

As best shown in FIG. 9, an inlet flow valve 150 in the fluid circuitmay be provided to selectively permit fluid at pump discharge pressureto flow back into the pump inlet 16 when the pump 10 is operating atspeeds wherein atmospheric pressure is insufficient to fill the inletport 16 of the pump 10 with fluid. This reduces cavitation and overcomesany restriction of fluid flow to the inlet 16 of the pump 10 or any lackof fluid potential energy. To accomplish this, the inlet flow valve 150may be a spool type valve slidably received in a bore 152 of a body,such as the pump housing 22, so that it is in communication with thefluid discharged from the pump outlet 18. As shown, the fluid circuitcomprises the pump 10, with the pump outlet 18 leading to an enginelubrication circuit 154 through a supply passage 156 which is connectedto the bore 152 containing the inlet flow valve 150. Downstream of theengine lubrication circuit 154, fluid is returned to a reservoir 112with a portion of such fluid routed through a pilot fluid passage 158leading to the inlet flow valve 150 to provide a pilot pressure signalon the inlet flow valve 150, if desired. A spring 159 may also beprovided to bias the inlet flow valve 150. From the reservoir, fluid issupplied through an inlet passage 160 to the inlet 16 of the fuel pump10. The inlet passage 160 can pass through the bore 152 containing theinlet flow valve 150 and is separated from the supply passage 156 by aland 162 of the inlet flow valve 150 which provides an essentially fluidtight seal with the body.

Accordingly, the fluid discharged from the pump 10 acts on the land 162by way of passage 156 in communication with from outlet line 157 andtends to displace the inlet flow valve 150 in a direction opposed by thespring 159 and the pilot pressure signal applied to the inlet flow valve150 through the pilot fluid passage 158. When the pressure of fluiddischarged from the pump 10 is high enough, to overcome the spring andpilot pressure from passage 158, the inlet flow valve 150 will bedisplaced so that its land 162 will be moved far enough to open theinlet passage 160 permitting communication between the supply passage156 and inlet passage 160 through the bore 152 and passage 161, as shownin FIG. 9. Thus, a portion of the fluid discharged from the pump 10 isfed back into the inlet 16 of the pump 10 along with fluid supplied fromthe reservoir 112 for the reasons stated above. This aspirated flow ofpressurized fluid into the inlet 16 supercharges the pump inlet toensure that the pump 10 is pumping liquid and not air or gas. Thisprevents cavitation and improves the pump efficiency and performance.

The purpose of the valve 150 and its supercharging effect is to convertavailable pressure energy into velocity energy at the inlet to providesupercharging.

Accordingly, the pump 10 incorporates many features which facilitate thedesign and operation of the pump, enable vastly improved control overthe pump operating parameters and output, and improve overall pumpperformance and efficiency. Desirably, the vane pump of the inventioncan meet the various requirements of lubrication for internal combustionengines at all speeds. Of course, the vane pump may also be utilized inpower transmission and other fluid distribution applications.

Finally, while preferred embodiments of the invention have beendescribed in some detail herein, the scope of the invention is definedby the claims which follow. Modifications of and applications for theinventive pump which are entirely within the spirit and scope of theinvention will be readily apparent to those skilled in the art.

1. A variable displacement vane pump, comprising: a housing defining achamber, a pump inlet through which fluid enters the housing and a pumpoutlet through which fluid is discharged from the housing underpressure; a containment ring or eccentric ring pivotally carried by thehousing for movement between a first position and a second position anddefining an opening with an internal surface; a rotor carried by thehousing for rotation relative to the internal surface and having aplurality of slots extending inwardly into the rotor from an exterior ofthe rotor; a plurality of vanes carried by the rotor with each vaneslidably received in a slot in the rotor; a first actuator responsive toapplication of fluid under pressure and operable to pivot thecontainment ring or eccentric ring in a first direction; a secondactuator responsive to application of fluid under pressure and operableto pivot the containment ring or eccentric ring in a second direction;wherein control and positioning of the first and second actuators are afunction of a combination of a first pressure signal and a secondpressure signal taken from discrete locations separated by a degree ofinherent hydraulic resistance in a downstream fluid circuit; an areadefining a fluid chamber formed between the housing and containment ringor eccentric ring with fluid under pressure in the fluid chamberdefining the first actuator; and a control valve responsive to thedifferential between the first pressure signal and the second pressuresignal to selectively apply, based on engine conditions, application offluid under pressure to either the first or second actuator based onengine conditions.
 2. The pump of claim 1 wherein the first actuator isa piston slidably carried by the housing.
 3. The variable displacementvane pump of claim 1 wherein said second direction is in a directionopposite of the first direction.
 4. The pump of claim 1 wherein thesecond actuator is a piston slidably carried by the housing.
 5. The pumpof claim 1 wherein the first actuator includes a spring that in yieldingbiases the containment ring or eccentric ring in the first direction. 6.The pump of claim 1 which also comprises a seal between the containmentring or eccentric ring and the housing.
 7. The pump of claim 1 whichalso comprises another fluid chamber defined at least in part by sealwith fluid under pressure in the another fluid chamber defining thesecond actuator.
 8. The pump of claim 1 which also comprises a pivot pinabout which the containment ring or eccentric ring pivots, the pivot pindefining a pivot axis of the containment ring or eccentric ring which isoffset from the axis of the rotor by about one-half the maximumeccentricity of the containment ring or eccentric ring relative to therotor.
 9. The pump of claim 1 which also comprises an inlet flow valveresponsive to a fluid pressure signal above a threshold pressure topermit a portion of fluid discharged from the pump outlet to flow intothe pump inlet during at least some fluid flow conditions.
 10. The pumpof claim 9 wherein the inlet flow valve is yieldably biased to aposition preventing fluid discharged from the pump outlet to flow intothe inlet of the pump and is displaced by a sufficiently high fluidpressure signal to a position permitting fluid discharged from the pumpoutlet to flow into the pump inlet.
 11. The pump of claim 1 which alsocomprises a vane extension member carried by the housing and engageablewith the vanes during at least certain positions of the rotor to ensurethat at least two vanes extend outwardly from the exterior of the rotorat all times.
 12. The pump of claim 11 wherein the vane extension memberis a ring carried by the rotor to engage at least two vanes at alltimes.
 13. The pump of claim 1 wherein the slots on the rotor extendradially inwardly of the rotor.
 14. The pump of claim 1 wherein the sealis defined by direct contact between the containment ring or eccentricring and the housing.
 15. The pump of claim 1 wherein the seal iscarried by the containment ring or eccentric ring.
 16. The pump of claim1 wherein the seal is carried on the housing.
 17. The pump of claim 10wherein fluid under pressure is communicated with the slots in the rotorto bias the vanes into contact with the cam surface.
 18. The pump ofclaim 11 wherein the vane extension member further comprises a ringportion for engaging the two vanes and oil pressure acting on the vanesfor extending the vanes outwardly.
 19. The pump of claim 1 which alsocomprises an exhaust opening in the housing through which fluid in thefluid chamber is discharged under certain fluid flow conditions andwherein the control valve controls fluid flow from the fluid chamberthrough the exhaust opening in response to certain fluid pressures ofsaid first and second pilot pressures.
 20. The pump of claim 1 whereinthe vanes have leading and trailing faces and the slots in the rotor areslightly wider than the vanes received in said slots so that a fluidfilm forms between the rotor and the leading and trailing faces of eachvane.
 21. The pump of claim 20 further comprises a seal between a vaneand the rotor to restrict fluid flow between them.
 22. The pump of claim21 wherein the seal is formed by contact between the vane and rotor. 23.The pump of claim 10 wherein the inlet flow valve is biased by a spring.24. The pump of claim 23 wherein the inlet flow valve is further biasedby a pilot pressure signal.
 25. A variable displacement vane-type fluidpump, comprising: a housing defining a pump inlet through which fluidenters the pump, a pump outlet from which fluid is discharged underpressure and a fluid chamber between the pump inlet and pump outlet; acontainment ring or eccentric ring pivotally carried by the housingwithin the fluid chamber for movement between a first position and asecond position, the containment ring or eccentric ring having aninterior opening with an internal surface; a rotor carried by thehousing at least in part in the interior opening of the containment ringor eccentric ring, driven for rotation relative to the internal surfaceand having a plurality of slots extending radially inwardly into therotor from an exterior of the rotor; a plurality of vanes carried by therotor with a vane slidably received in each slot in the rotor; a firstactuator responsive to a first fluid pressure and operable to pivot thecontainment ring or eccentric ring toward its first position; a secondactuator responsive to a second fluid pressure and operable to pivot thecontainment ring or eccentric ring toward its second position; a controlvalve responsive to the differential between a first pressure signal anda second pressure signal to selectively apply, based on engineconditions, application of fluid under pressure to either the first orsecond actuator based on engine conditions; wherein control andpositioning of the first and second actuators are a function of acombination of the first pressure signal and the second pressure signaltaken from discrete locations separated by a degree of inherenthydraulic resistance in a downstream fluid; and an area defining fluidchamber form d between the housing and containment ring or eccentricring with fluid under pressure in the fluid chamber defining the firstactuator.
 26. A variable displacement vane-type fluid pump, comprising:a housing defining a pump inlet through which fluid enters the pump, apump outlet from which fluid is discharged under pressure and a fluidchamber between the pump inlet and pump outlet; a containment ring oreccentric ring pivotally carried by the housing for movement between afirst position and a second position and defining an internal surface; arotor carried by the housing in the fluid chamber for rotation relativeto the internal surface and having a plurality of slots extendinginwardly into the rotor from an exterior of the rotor; a plurality ofvanes carried by the rotor with a vane slidably received in each slot inthe rotor; a first actuator responsive to a first control pressure andoperable to pivot the containment ring or eccentric ring in a firstdirection; a second actuator responsive to a second control pressure andoperable to pivot the containment ring or eccentric ring in a seconddirection; a control valve responsive to a control pilot pressure tocontrol application of the first fluid pressure to the first actuator,and responsive to a second control pressure to control application ofthe second fluid pressure to the second actuator; and a vane extensionmember carried by the housing and engageable with the vanes during atleast certain positions of the rotor to ensure that at least one vaneextends outwardly from the exterior of the rotor at all times.
 27. Thevariable displacement vane-type fluid pump of claim 26 wherein the firstactuator is a chamber formed between a portion of the containment ringand a portion of the housing.
 28. A variable displacement vane-typefluid pump, comprising: a housing defining a pump inlet through whichfluid enters the pump, a pump outlet from which fluid is dischargedunder pressure and a fluid chamber between the pump inlet and pumpoutlet; a containment ring or eccentric ring pivotally carried by thehousing within the fluid chamber for movement between a first positionand a second position, the containment ring or eccentric ring having aninterior opening with an internal surface; a rotor carried by thehousing at least in part in the interior opening of the containment ringor eccentric ring, driven for rotation relative to the internal surfaceand having a plurality of slots extending radially inwardly into therotor from an exterior of the rotor; a plurality of vanes carried by therotor with a vane slidably received in each slot in the rotor; a firstactuator responsive to a first control pressure and operable to pivotthe containment ring or eccentric ring toward its first position; asecond actuator responsive to a second control pressure and operable topivot the containment ring or eccentric ring toward its second position;a control circuit responsive to engine conditions for providing avariable targeting of pump output wherein pressure from the oil circuitin the engine acts on the first actuator and pressure from the outletacts on the second actuator for variable control of the containment ringin response to these conditions; wherein control and positioning of thefirst and second actuators are a function of a combination of a firstpressure signal and a second pressure signal taken from discretelocations separated by a degree of inherent hydraulic resistance in adownstream fluid circuit; an area defining a fluid chamber formedbetween the housing and containment ring or eccentric ring with fluidunder pressure in the fluid chamber defining the first actuator; and acontrol valve responsive to the differential between the first pressuresignal and the second pressure signal to selectively apply, based onengine conditions, application of fluid under pressure to either thefirst or second actuator based on engine conditions.
 29. The variabledisplacement vane-type fluid pump of claim 28 wherein the controlcircuit includes an actuator operatively connected to one of theactuators for moving the containment ring in response to the controlpressures.
 30. A variable displacement vane pump, comprising: a housingdefining a chamber, a pump inlet through which fluid enters the housingand a pump outlet through which fluid is discharged from the housingunder pressure; a containment ring or eccentric ring pivotally carriedby the housing for movement between a first position and a secondposition and defining an opening with an internal surface; a rotorcarried by the housing for rotation relative to the internal surface andhaving a plurality of slots extending inwardly into the rotor from anexterior of the rotor; a plurality of vanes carried by the rotor witheach vane slidably received in a slot in the rotor; a first actuatorresponsive to application of fluid under pressure and operable to pivotthe containment ring or eccentric ring in a first direction; a secondactuator responsive to application of fluid under pressure and operableto pivot the containment ring or eccentric ring in a second direction;wherein the first and second actuators are fluid acting directly on thecontainment ring; wherein control and positioning of the first andsecond actuators are a function of a combination of a first pressuresignal and a second pressure signal taken from discrete locationsseparated by a degree of inherent hydraulic resistance in a downstreamfluid circuit; an area defining a fluid chamber formed between thehousing and containment ring or eccentric ring with fluid under pressurein the fluid chamber defining the first actuator; and a control valveresponsive to the differential between the first pressure signal and thesecond pressure signal to selectively apply, based on engine conditions,application of fluid under pressure to either the first or secondactuator based on engine conditions.
 31. A variable displacement vanepump, comprising: a housing defining a chamber, a pump inlet throughwhich fluid enters the housing and a pump outlet through which fluid isdischarged from the housing under pressure; a containment ring oreccentric ring pivotally carried by the housing for movement between afirst position and a second position and defining an opening with aninternal surface; a rotor carried by the housing for rotation relativeto the internal surface and having a plurality of slots extendinginwardly into the rotor from an exterior of the rotor; a plurality ofvanes carried by the rotor with each vane slidably received in a slot inthe rotor; a first actuator responsive to application of fluid underpressure and operable to pivot the containment ring or eccentric ring ina first direction; a second actuator responsive to application of fluidunder pressure and operable to pivot the containment ring or eccentricring in a second direction; a seal between the containment ring oreccentric ring and the housing defining a fluid chamber between thehousing and containment ring or eccentric ring with fluid under pressurein the fluid chamber defining the first actuator; another fluid chamberdefined at least in part by the seal with fluid under pressure in theanother fluid chamber defining the second; and a control valveresponsive to the differential between the first pressure signal and thesecond pressure signal to selectively apply, based on engine conditions,application of fluid under pressure to either the first or secondactuator based on engine conditions.
 32. The pump of claim 31 which alsocomprises an inlet flow valve responsive to a fluid pressure signalabove a threshold pressure to permit a portion of fluid discharged fromthe pump outlet to flow into the pump inlet during at least some fluidflow conditions.
 33. The pump of claim 32 wherein the inlet flow valveis yieldably biased to a position preventing fluid discharged from thepump outlet to flow into the inlet of the pump and is displaced by asufficiently high fluid pressure signal to a position permitting fluiddischarged from the pump outlet to flow into the pump inlet.
 34. Thepump of claim 31 which also comprises a vane extension member carried bythe housing and engageable with the vanes during at least certainpositions of the rotor to ensure that at least two vanes extendoutwardly from the exterior of the rotor at all times.
 35. The pump ofclaim 34 wherein the vane extension member is a ring carried by therotor to engage at least two vanes at all times.
 36. The pump of claim31 wherein the seal is carried by the containment ring or eccentricring.
 37. The pump of claim 33 wherein fluid under pressure iscommunicated with the slots in the rotor to bias the vanes into contactwith the cam surface.
 38. The pump of claim 37 wherein the vaneextension member further comprises a ring portion for engaging the tworings and oil pressure acting on the vanes for extending the vaneoutwardly.
 39. The pump of claim 33 wherein the inlet flow valve isbiased by a spring.
 40. The pump of claim 39 wherein the inlet flowvalve is further biased by a pilot pressure signal.
 41. A variabledisplacement vane pump, comprising: a housing defining a chamber, a pumpinlet through which fluid enters the housing and a pump outlet throughwhich fluid is discharged from the housing under pressure; a containmentring or eccentric ring pivotally carried by the housing for movementbetween a first position and a second position and defining an openingwith an internal surface; a rotor carried by the housing for rotationrelative to the internal surface and having a plurality of slotsextending inwardly into the rotor from an exterior of the rotor, aplurality of vanes carried by the rotor with each vane slidably receivedin a slot in the rotor; a first actuator responsive to application offluid under pressure and operable to pivot the containment ring oreccentric ring in a first direction; a second actuator responsive toapplication of fluid under pressure and operable to pivot thecontainment ring or eccentric ring in a second direction; and an inletflow valve responsive to a fluid pressure signal above a thresholdpressure to permit a portion of fluid discharged from the pump outlet toflow into the pump inlet during at least some fluid flow conditions. 42.The pump of claim 41 wherein the inlet flow valve is yieldably biased toa position preventing fluid discharged from the pump outlet to flow intothe inlet of the pump and is displaced by a sufficiently high fluidpressure signal to a position permitting fluid discharged from the pumpoutlet to flow into the pump inlet.
 43. The pump of claim 41 which alsocomprises a vane extension member carried by the housing and engageablewith the vanes during at least certain positions of the rotor to ensurethat at least two vanes extend outwardly from the exterior of the rotorat all times.
 44. The pump of claim 43 wherein the vane extension memberis a ring carried by the rotor to engage at least two vanes at alltimes.
 45. The pump of claim 41 wherein the slots on the rotor extendradially inwardly of the rotor.
 46. The pump of claim 42 wherein fluidunder pressure is communicated with the slots in the rotor to bias thevanes into contact with the cam surface.
 47. The pump of claim 43wherein the vane extension member further comprises a ring portion forengaging the two rings and oil pressure acting on the vanes forextending the vane outwardly.
 48. The pump of claim 41 wherein the vaneshave leading and trailing faces and the slots in the rotor are slightlywider than the vanes received in the slots so that a fluid film formsbetween the rotor and the leading and trailing faces of each vane. 49.The pump of claim 48 further comprising a seal between a vane and therotor to restrict fluid flow between them.
 50. The pump of claim 49wherein the seal is formed by contact between the vane and rotor. 51.The pump of claim 42 wherein the inlet flow valve is biased by a spring.52. The pump of claim 51 wherein the inlet flow valve is further biasedby a pilot pressure signal.
 53. A variable displacement vane pump,comprising: a housing defining a chamber, a pump inlet through whichfluid enters the housing and a pump outlet through which fluid isdischarged from the housing under pressure; a containment ring oreccentric ring pivotally carried by the housing for movement between afirst position and a second position and defining an opening with aninternal surface; a rotor carried by the housing for rotation relativeto the internal surface and having a plurality of slots extendinginwardly into the rotor from an exterior of the rotor; a plurality ofvanes carried by the rotor with each vane slidably received in a slot inthe rotor; a first actuator responsive to application of fluid underpressure and operable to pivot the containment ring or eccentric ring ina first direction; a second actuator responsive to application of fluidunder pressure and operable to pivot the containment ring or eccentricring in a second direction; and a vane extension member carried by thehousing and engageable with the vanes during at least certain positionsof the rotor to ensure that at least two vanes extend outwardly from theexterior of the rotor at all times.
 54. The pump of claim 53 wherein thevane extension member is a ring carried by the rotor to engage at leasttwo vanes at all times.
 55. The pump of claim 53 wherein the slots onthe rotor extend radially inwardly of the rotor.
 56. The pump of claim53 wherein the vane extension member further comprises a ring portionfor engaging the two rings and oil pressure acting on the vanes forextending the vane outwardly.
 57. The pump of claim 53 wherein the vaneshave leading and trailing faces and the slots in the rotor are slightlywider than the vanes received in the slots so that a fluid film formsbetween the rotor and the leading and trailing faces of each vane. 58.The pump of claim 57 further comprising a seal between a vane and therotor to restrict fluid flow between them.
 59. The pump of claim 58wherein the seal is formed by contact between the vane and rotor.
 60. Avariable displacement vane pump, comprising: a housing defining achamber, a pump inlet through which fluid enters the housing and a pumpoutlet through which fluid is discharged from the housing underpressure; a containment ring or eccentric ring pivotally carried by thehousing for movement between a first position and a second position anddefining an opening with an internal surface; a rotor carried by thehousing for rotation relative to the internal surface and having aplurality of slots extending inwardly into the rotor from an exterior ofthe rotor; a plurality of vanes carried by the rotor with each vaneslidably received in a slot in the rotor; a first actuator responsive toapplication of fluid under pressure and operable to pivot thecontainment ring or eccentric ring in a first direction, wherein thefirst actuator is responsive to a first actuation pressure signal; asecond actuator responsive to application of fluid under pressure andoperable to pivot the containment ring or eccentric ring in a seconddirection, wherein the second actuator is responsive to a secondactuation pressure signal; an area defining a fluid chamber formedbetween the housing and containment ring or eccentric ring with fluidunder pressure in the fluid chamber defining the first actuator; and acontrol valve responsive to the differential between the first pressuresignal and the second pressure signal to selectively apply, based onengine conditions, application of fluid under pressure to either thefirst or second actuator based on engine conditions.
 61. The pump ofclaim 60 wherein the first actuator is a piston slidably carried by thehousing.
 62. The variable displacement vane pump of claim 60 wherein thesecond direction is in a direction opposite of the first direction. 63.The pump of claim 60 wherein the second actuator is a piston slidablycarried by the housing.
 64. The pump of claim 60 wherein the firstactuator includes a spring that in yielding biases the containment ringor eccentric ring in the first direction.
 65. The pump of claim 60 whichalso comprises another fluid chamber defined at least in part by theseal with fluid under pressure in the another fluid chamber defining thesecond actuator.
 66. The pump of claim 60 which also comprises a controlvalve responsive to a first fluid pressure signal to control applicationof the fluid under pressure to the first actuator, and responsive to asecond fluid pressure signal to control application of the fluid underpressure to the second actuator.
 67. The pump of claim 60 which alsocomprises a pivot pin about which the containment ring or eccentric ringpivots, the pivot pin defining a pivot axis of the containment ring oreccentric ring which is offset from the axis of the rotor by aboutone-half the maximum eccentricity of the containment ring or eccentricring relative to the rotor.
 68. The pump of claim 60 which alsocomprises an inlet flow valve responsive to a fluid pressure signalabove a threshold pressure to permit a portion of fluid discharged fromthe pump outlet to flow into the pump inlet during at least some fluidflow conditions.
 69. The pump of claim 68 wherein the inlet flow valveis yieldably biased to a position preventing fluid discharged from thepump outlet to flow into the inlet of the pump and is displaced by asufficiently high fluid pressure signal to a position permitting fluiddischarged from the pump outlet to flow into the pump inlet.
 70. Thepump of claim 60 which also comprises a vane extension member carried bythe housing and engageable with the vanes during at least certainpositions of the rotor to ensure that at least two vanes extendoutwardly from the exterior of the rotor at all times.
 71. The pump ofclaim 70 wherein the vane extension member is a ring carried by therotor to engage at least two vanes at all times.
 72. The pump of claim60 wherein the slots on the rotor extend radially inwardly of the rotor.73. The pump of claim 60 wherein the seal is defined by direct contactbetween the containment ring or eccentric ring and the housing.
 74. Thepump of claim 60 wherein the seal is carried by the containment ring oreccentric ring.
 75. The pump of claim 60 wherein the seal is carried onthe housing.
 76. The pump of claim 69 wherein fluid under pressure iscommunicated with the slots in the rotor to bias the vanes into contactwith the cam surface.
 77. The pump of claim 70 wherein the vaneextension member further comprises a ring portion for engaging the tworings and oil pressure acting on the vanes for extending the vaneoutwardly.
 78. The pump of claim 66 which also comprises an exhaustopening in the housing through which fluid in the fluid chamber isdischarged under certain fluid flow conditions and wherein the controlvalve controls fluid flow from the fluid chamber through the exhaustopening in response to certain fluid pressures of the first and secondpilot pressures.
 79. The pump of claim 60 wherein the vanes have leadingand trailing faces and the slots in the rotor are slightly wider thanthe vanes received in the slots so that a fluid film forms between therotor and the leading and trailing faces of each vane.
 80. The pump ofclaim 79 further comprising a seal between a vane and the rotor torestrict fluid flow between them.
 81. The pump of claim 80 wherein theseal is formed by contact between the vane and rotor.
 82. The pump ofclaim 69 wherein the inlet flow valve is biased by a spring.
 83. Thepump of claim 82 wherein the inlet flow valve is further biased by apilot pressure signal.
 84. A variable displacement pump system,comprising: a pump assembly including a pump inlet through which fluidenters the housing and a pump outlet through which fluid is dischargedfrom the pump assembly under pressure; a first actuator responsive toapplication of fluid under pressure and operable to cause displacementof the pump assembly towards a first displacement position; a secondactuator responsive to application of fluid under pressure and operableto cause displacement of the pump assembly towards a second displacementposition; wherein control and positioning of the first and secondactuators are a function of a combination of a first pressure signal anda second pressure signal taken from discrete locations separated by adegree of inherent hydraulic resistance in a downstream fluid circuit;an area defining a fluid chamber formed between the housing andcontainment ring or eccentric ring with fluid under pressure in thefluid chamber defining the first actuator; and a control valveresponsive to the differential between the first pressure signal and thesecond pressure signal to selectively apply, based on engine conditions,application of fluid under pressure to either the first or secondactuator based on engine conditions.
 85. The pump of claim 84 which alsocomprises an inlet flow valve responsive to a fluid pressure signalabove a threshold pressure to permit a portion of fluid discharged fromthe pump outlet to flow into the pump inlet during at least some fluidflow conditions.
 86. The pump of claim 85 wherein the inlet flow valveis yieldably biased to a position preventing fluid discharged from thepump outlet to flow into the inlet of the pump and is displaced by asufficiently high fluid pressure signal to a position permitting fluiddischarged from the pump outlet to flow into the pump inlet.
 87. Thepump of claim 84 which also comprises an exhaust opening in the housingthrough which fluid in the fluid chamber is discharged under certainfluid flow conditions and wherein the control valve controls fluid flowfrom the fluid chamber through the exhaust opening in response tocertain fluid pressure signals of the first and second pilot pressuresignals.
 88. The pump of claim 86 wherein the inlet flow valve is biasedby a spring.
 89. The pump of claim 88 wherein the inlet flow valve isfurther biased by a pilot pressure signal.
 90. A variable displacementpump system, comprising: a pump assembly including a pump inlet throughwhich fluid enters the housing and a pump outlet through which fluid isdischarged from the pump assembly under pressure; a first actuatorresponsive to application of fluid under pressure and operable to causedisplacement of the pump assembly towards a first displacement position;and a second actuator responsive to application of fluid under pressureand operable to cause displacement of the pump assembly towards a seconddisplacement position; a flow control valve for mechanically varying thepump displacement; a compression spring connectable at a first springend to a spool of the flow control valve, wherein the compression springmaintains pressure on the flow control valve during regular operation,and provides return pressure in the absence of a pilot pressure on theflow control valve; a target piston connected to the second end of thecompression spring, wherein the target piston exerts a force on thecompression spring; wherein control and positioning of the first andsecond actuators are a function of a combination of a first pressuresignal and a second pressure signal taken from discrete locationsseparated by a degree of inherent hydraulic resistance in a downstreamfluid circuit acting on the target piston and the flow control valve forproviding a variable pressure target for regulation of the pump'sdisplacement in response to varying engine speeds; and an area defininga fluid chamber formed between the housing and containment ring oreccentric ring with fluid under pressure in the fluid chamber definingthe first actuator; wherein the flow control valve is responsive to thedifferential between the first pressure signal and the second pressuresignal to selectively apply, based on engine conditions, application offluid under pressure to either the first or second actuator based onengine conditions.
 91. The pump of claim 90 wherein the target piston ispositioned in a bore, the target piston being located on a first side bya pressure from a control input and on a second side by a groundedspring, the position in the bore acting as a reference for a regulationsystem to provide a predetermined regulation target pressure in thefluid circuit.
 92. The pump of claim 91 wherein a multifunctional valveprovides for varying the displacement of the pump by directingpressurized fluid to an on-stroke or de-stroke side of the pump assemblyin response to the target piston acting on the multifunctional valve ina first direction, and a pressure input from the fluid circuit acting onthe multifunctional valve in a second direction.
 93. The pump of claim92 wherein the multifunctional valve is a spool type valve having abiasing spring connected between the target piston and a spool valve,the target piston compressing the spring and biasing the spool valve forproviding a target position in response to a control input from the pumpassembly, the spool valve having passages for directing a control flowof fluid to the pump assembly, a control pressure from the fluid circuitacting on the spool valve against the biasing spring for seeking apredetermined target pressure.
 94. A variable displacement vane pump,comprising: a housing defining a chamber, a pump inlet through whichfluid enters the housing and a pump outlet through which fluid isdischarged from the housing under pressure; a containment ring oreccentric ring pivotally carried by the housing for movement between afirst position and a second position and defining an opening with aninternal surface; a rotor carried by the housing for rotation relativeto the internal surface and having a plurality of slots extendinginwardly into the rotor from an exterior of the rotor; a plurality ofvanes carried by the rotor with each vane slidably received in a slot inthe rotor; a first actuator responsive to application of fluid underpressure and operable to pivot the containment ring or eccentric ring ina first direction; a second actuator responsive to application of fluidunder pressure and operable to pivot the containment ring or eccentricring in a second direction; wherein control and positioning of the firstand second actuators are a function of a combination of a first pressuresignal and a second pressure signal taken from discrete locationsseparated by a degree of inherent hydraulic resistance in a downstreamfluid circuit; and a vane extension member carried by the housing andengageable with the vanes during at least certain positions of the rotorto ensure that at least two vanes extend outwardly from the exterior ofthe rotor at all times.
 95. The pump of claim 94 wherein the firstactuator is a piston slidably carried by the housing.
 96. The variabledisplacement vane pump of claim 94 wherein the second direction is in adirection opposite of the first direction.
 97. The pump of claim 94wherein the second actuator is a piston slidably carried by the housing.98. The pump of claim 94 wherein the first actuator includes a springthat in yielding biases the containment ring or eccentric ring in thefirst direction.
 99. The pump of claim 94 which also comprises a sealbetween the containment ring or eccentric ring and the housing defininga fluid chamber between the housing and containment ring or eccentricring with fluid under pressure in the fluid chamber defining the firstactuator.
 100. The pump of claim 99 which also comprises another fluidchamber defined at least in part by the seal with fluid under pressurein the another fluid chamber defining the second actuator.
 101. The pumpof claim 94 which also comprises a control valve responsive to a firstfluid pressure signal to control application of the fluid under pressureto the first actuator, and responsive to a second fluid pressure signalto control application of the fluid under pressure to the secondactuator.
 102. The pump of claim 94 which also comprises a pivot pinabout which the containment ring or eccentric ring pivots, the pivot pindefining a pivot axis of the containment ring or eccentric ring which isoffset from the axis of the rotor by about one-half the maximumeccentricity of the containment ring or eccentric ring relative to therotor.
 103. The pump of claim 94 which also comprises an inlet flowvalve responsive to a fluid pressure signal above a threshold pressureto permit a portion of fluid discharged from the pump outlet to flowinto the pump inlet during at least some fluid flow conditions.
 104. Thepump of claim 103 wherein the inlet flow valve is yieldably biased to aposition preventing fluid discharged from the pump outlet to flow intothe inlet of the pump and is displaced by a sufficiently high fluidpressure signal to a position permitting fluid discharged from the pumpoutlet to flow into the pump inlet.
 105. The pump of claim 94 whereinthe vane extension member is a ring carried by the rotor to engage atleast two vanes at all times.
 106. The pump of claim 94 wherein theslots on the rotor extend radially inwardly of the rotor.
 107. The pumpof claim 99 wherein the seal is defined by direct contact between thecontainment ring or eccentric ring and the housing.
 108. The pump ofclaim 99 wherein the seal is carried by the containment ring oreccentric ring.
 109. The pump of claim 99 wherein the seal is carried onthe housing.
 110. The pump of claim 104 wherein fluid under pressure iscommunicated with the slots in the rotor to bias the vanes into contactwith the cam surface.
 111. The pump of claim 94 wherein the vaneextension member further comprises a ring portion for engaging the tworings and oil pressure acting on the vanes for extending the vaneoutwardly.
 112. The pump of claim 101 which also comprises an exhaustopening in the housing through which fluid in the fluid chamber isdischarged under certain fluid flow conditions and wherein the controlvalve controls fluid flow from the fluid chamber through the exhaustopening in response to certain fluid pressures of the first and secondpilot pressures.
 113. The pump of claim 94 wherein the vanes haveleading and trailing faces and the slots in the rotor are slightly widerthan the vanes received in the slots so that a fluid film forms betweenthe rotor and the leading and trailing faces of each vane.
 114. The pumpof claim 113 further comprising a seal between a vane and the rotor torestrict fluid flow between them.
 115. The pump of claim 114 wherein theseal is formed by contact between the vane and rotor.
 116. The pump ofclaim 104 wherein the inlet flow valve is biased by a spring.
 117. Thepump of claim 116 wherein the inlet flow valve is further biased by apilot pressure signal.
 118. A variable displacement vane pump,comprising: a housing defining a chamber, a pump inlet through whichfluid enters the housing and a pump outlet through which fluid isdischarged from the housing under pressure; a containment ring oreccentric ring pivotally carried by the housing for movement between afirst position and a second position and defining an opening with aninternal surface; a rotor carried by the housing for rotation relativeto the internal surface and having a plurality of slots extendinginwardly into the rotor from an exterior of the rotor; a plurality ofvanes carried by the rotor with each vane slidably received in a slot inthe rotor; a first actuator responsive to application of fluid underpressure and operable to pivot the containment ring or eccentric ring ina first direction; a second actuator responsive to application of fluidunder pressure and operable to pivot the containment ring or eccentricring in a second direction; a seal between the containment ring oreccentric ring and the housing defining a fluid chamber between thehousing and containment ring or eccentric ring with fluid under pressurein the fluid chamber defining the first actuator; and another fluidchamber defined at least in part by the seal with fluid under pressurein the another fluid chamber defining the second actuator.
 119. The pumpof claim 118 which also comprises an inlet flow valve responsive to afluid pressure signal above a threshold pressure to permit a portion offluid discharged from the pump outlet to flow into the pump inlet duringat least some fluid flow conditions.
 120. The pump of claim 119 whereinthe inlet flow valve is yieldably biased to a position preventing fluiddischarged from the pump outlet to flow into the inlet of the pump andis displaced by a sufficiently high fluid pressure signal to a positionpermitting fluid discharged from the pump outlet to flow into the pumpinlet.
 121. The pump of claim 118 which also comprises a vane extensionmember carried by the housing and engageable with the vanes during atleast certain positions of the rotor to ensure that at least two vanesextend outwardly from the exterior of the rotor at all times.
 122. Thepump of claim 121 wherein the vane extension member is a ring carried bythe rotor to engage at least two vanes at all times.
 123. The pump ofclaim 118 wherein the seal is carried by the containment ring oreccentric ring.
 124. The pump of claim 120 wherein fluid under pressureis communicated with the slots in the rotor to bias the vanes intocontact with the cam surface.
 125. The pump of claim 124 wherein thevane extension member further comprises a ring portion for engaging thetwo rings and oil pressure acting on the vanes for extending the vaneoutwardly.
 126. The pump of claim 120 wherein the inlet flow valve isbiased by a spring.
 127. The pump of claim 126 wherein the inlet flowvalve is further biased by a pilot pressure signal.
 128. A variabledisplacement vane pump, comprising: a housing defining a chamber, a pumpinlet through which fluid enters the housing and a pump outlet throughwhich fluid is discharged from the housing under pressure; a containmentring or eccentric ring pivotally carried by the housing for movementbetween a first position and a second position and defining an openingwith an internal surface; a rotor carried by the housing for rotationrelative to the internal surface and having a plurality of slotsextending inwardly into the rotor from an exterior of the rotor; aplurality of vanes carried by the rotor with each vane slidably receivedin a slot in the rotor; a first actuator responsive to application offluid under pressure and operable to pivot the containment ring oreccentric ring in a first direction, wherein the first actuator isresponsive to a first actuation pressure signal; a second actuatorresponsive to application of fluid under pressure and operable to pivotthe containment ring or eccentric ring in a second direction, whereinthe second actuator is responsive to a second actuation pressure signal;and an inlet flow valve responsive to a fluid pressure signal above athreshold pressure to permit a portion of fluid discharged from the pumpoutlet to flow into the pump inlet during at least some fluid flowconditions.
 129. The pump of claim 128 wherein the first actuator is apiston slidably carried by the housing.
 130. The variable displacementvane pump of claim 128 wherein the second direction is in a directionopposite of the first direction.
 131. The pump of claim 128 wherein thesecond actuator is a piston slidably carried by the housing.
 132. Thepump of claim 128 wherein the first actuator includes a spring that inyielding biases the containment ring or eccentric ring in the firstdirection.
 133. The pump of claim 128 which also comprises a sealbetween the containment ring or eccentric ring and the housing defininga fluid chamber between the housing and containment ring or eccentricring with fluid under pressure in the fluid chamber defining the firstactuator.
 134. The pump of claim 133 which also comprises another fluidchamber defined at least in part by the seal with fluid under pressurein the another fluid chamber defining the second actuator.
 135. The pumpof claim 128 which also comprises a control valve responsive to a firstfluid pressure signal to control application of the fluid under pressureto the first actuator, and responsive to a second fluid pressure signalto control application of the fluid under pressure to the secondactuator.
 136. The pump of claim 128 which also comprises a pivot pinabout which the containment ring or eccentric ring pivots, the pivot pindefining a pivot axis of the containment ring or eccentric ring which isoffset from the axis of the rotor by about one-half the maximumeccentricity of the containment ring or eccentric ring relative to therotor.
 137. The pump of claim 128 wherein the inlet flow valve isyieldably biased to a position preventing fluid discharged from the pumpoutlet to flow into the inlet of the pump and is displaced by asufficiently high fluid pressure signal to a position permitting fluiddischarged from the pump outlet to flow into the pump inlet.
 138. Thepump of claim 128 which also comprises a vane extension member carriedby the housing and engageable with the vanes during at least certainpositions of the rotor to ensure that at least two vanes extendoutwardly from the exterior of the rotor at all times.
 139. The pump ofclaim 138 wherein the vane extension member is a ring carried by therotor to engage at least two vanes at all times.
 140. The pump of claim128 wherein the slots on the rotor extend radially inwardly of therotor.
 141. The pump of claim 133 wherein the seal is defined by directcontact between the containment ring or eccentric ring and the housing.142. The pump of claim 133 wherein the seal is carried by thecontainment ring or eccentric ring.
 143. The pump of claim 133 whereinthe seal is carried on the housing.
 144. The pump of claim 137 whereinfluid under pressure is communicated with the slots in the rotor to biasthe vanes into contact with the cam surface.
 145. The pump of claim 138wherein the vane extension member further comprises a ring portion forengaging the two rings and oil pressure acting on the vanes forextending the vane outwardly.
 146. The pump of claim 135 which alsocomprises an exhaust opening in the housing through which fluid in thefluid chamber is discharged under certain fluid flow conditions andwherein the control valve controls fluid flow from the fluid chamberthrough the exhaust opening in response to certain fluid pressures ofthe first and second pilot pressures.
 147. The pump of claim 128 whereinthe vanes have leading and trailing faces and the slots in the rotor areslightly wider than the vanes received in the slots so that a fluid filmforms between the rotor and the leading and trailing faces of each vane.148. The pump of claim 147 further comprising a seal between a vane andthe rotor to restrict fluid flow between them.
 149. The pump of claim148 wherein the seal is formed by contact between the vane and rotor.150. The pump of claim 137 wherein the inlet flow valve is biased by aspring.
 151. The pump of claim 150 wherein the inlet flow valve isfurther biased by a pilot pressure signal.
 152. A variable displacementpump system, comprising: a pump assembly including a pump inlet throughwhich fluid enters the housing and a pump outlet through which fluid isdischarged from the pump assembly under pressure; a first actuatorresponsive to application of fluid under pressure and operable to causedisplacement of the pump assembly towards a first displacement position;a second actuator responsive to application of fluid under pressure andoperable to cause displacement of the pump assembly towards a seconddisplacement position; wherein control and positioning of the first andsecond actuators are a function of a combination of a first pressuresignal and a second pressure signal taken from discrete locationsseparated by a degree of inherent hydraulic resistance in a downstreamfluid circuit; and an inlet flow valve responsive to a fluid pressuresignal above a threshold pressure to permit a portion of fluiddischarged from the pump outlet to flow into the pump inlet during atleast some fluid flow conditions.
 153. The pump of claim 152 which alsocomprises a control valve responsive to a first and a second pressuresignal to control application of fluid pressure to the first and secondactuators.
 154. The pump of claim 152 wherein the inlet flow valve isyieldably biased to a position preventing fluid discharged from the pumpoutlet to flow into the inlet of the pump and is displaced by asufficiently high fluid pressure signal to a position permitting fluiddischarged from the pump outlet to flow into the pump inlet.
 155. Thepump of claim 152 which also comprises an exhaust opening in the housingthrough which fluid in the fluid chamber is discharged under certainfluid flow conditions and wherein the control valve controls fluid flowfrom the fluid chamber through the exhaust opening in response tocertain fluid pressures of the first and second pilot pressures. 156.The pump of claim 154 wherein the inlet flow valve is biased by aspring.
 157. The pump of claim 156 wherein the inlet flow valve isfurther biased by a pilot pressure signal.
 158. A variable displacementpump system, comprising: a pump assembly including a pump inlet throughwhich fluid enters the housing and a pump outlet through which fluid isdischarged from the pump assembly under pressure; a first actuatorresponsive to application of fluid under pressure and operable to causedisplacement of the pump assembly towards a first displacement position;and a second actuator responsive to application of fluid under pressureand operable to cause displacement of the pump assembly towards a seconddisplacement position; a flow control valve for mechanically varying thepump displacement; a compression spring connectable at a first springend to a spool of the flow control valve, wherein the compression springmaintains pressure on the flow control valve during regular operation,and provides return pressure in the absence of a pilot pressure on theflow control valve; and a target piston connected to the second end ofthe compression spring, wherein the target piston exerts a force on thecompression spring; wherein control and positioning of the first andsecond actuators are a function of a combination of a first pressuresignal and a second pressure signal taken from discrete locationsseparated by a degree of inherent hydraulic resistance in a downstreamfluid circuit acting on the target piston and the flow control valve forproviding a variable pressure target for regulation of the pump'sdisplacement in response to varying engine speeds; wherein the targetpiston is positioned in a bore, the target piston being located on afirst side by a pressure from a control input and on a second side by agrounded spring, the position in the bore acting as a reference for aregulation system to provide a predetermined regulation target pressurein the fluid circuit.
 159. The pump of claim 158 wherein amultifunctional valve provides for varying the displacement of the pumpby directing pressurized fluid to an on-stroke or de-stroke side of thepump assembly in response to the target piston acting on themultifunctional valve in a first direction, and a pressure input fromthe fluid circuit acting on the multifunctional valve in a seconddirection.
 160. The pump of claim 159 wherein the multifunctional valveis a spool type valve having a biasing spring connected between thetarget piston and a spool valve, the target piston compressing thespring and biasing the spool valve for providing a target position inresponse to a control input from the pump assembly, the spool valvehaving passages for directing a control flow of fluid to the pumpassembly, a control pressure from the fluid circuit acting on the spoolvalve against the biasing spring for seeking a predetermined targetpressure.